curl check url status

Recently we need to check our Route 53 accessibility before invalidating our cache in CDN. So need to add this logic into our Jenkins job. The command :

Angular Rxjs Error Handling flow

In Angular 2+, http are all RX based. so the error flow is quite different from what we used to have in angular 1.x’s promise based way. consider the code So the basic flow is if anything exception happened, the error handler function in the catch block will be called first. That function should return an…

How SSL works

Simple version Your web browser downloads the web server’s certificate, which contains the public key of the web server. This certificate is signed with the private key of a trusted certificate authority. Your web browser comes installed with the public keys of all of the major certificate authorities. It uses this public key to verify…

meta tag “HTTP=EQUIV”

By using the so called HTTP-EQUIV tag you are able to add certain values to your website. HTTP-EQUIV meta tags define the header of an HTML document. This is a section of code that is sent to your browser before the rest of the page. It communicates to your browser certain introductory information about the…

What happens when you type a web page address in the address bar

Your browser, if it doesn’t already know, will ask your OS’s DNS system what the address (IP address) of the host (“www.google.com,” for example) is. If your OS doesn’t know, it will query third-party DNS servers (those of your ISP, for example). Once an address is obtained, your web browser establishes a TCP/IP socket connection,…

Why is apache used in front of tomcat

Performance – If you have a lot of static content, serving it with Apache will improve your performance. If most of your content is dynamic, using Tomcat or Glassfish alone will be just as fast (probably faster). Scalability – You can load balance multiple instances of your application behind Apache. This will allow you to handle more…

vps centos use tomcat as default http server

stop apache: service httpd stop start tomcat: service tomcat start in tomcat’s server.xml change the listing port to 80;  User netstat -ntplau   to check the active listening port.  All services are in /etc/init.d